Advances in electrochemistry have given users of portable electronic systems a wide range of choice for power sources. Examples of such power sources include batteries, capacitors, and hybrid battery-capacitor systems. As a result, manufacturers of portable electronic devices, such as portable two way radios, for example, offer several styles of batteries for the same device. A typical battery family for a two-way radio includes three chemical systems, each system offering 2 or 3 capacities. Each of these batteries has different charging requirements when charged. Accordingly a battery charger designed for a given battery family has to be quite sophisticated.
This is especially true if designers of the charger take into consideration future battery designs. When a customer purchases a charger the charge process programmed into the charger is the best current technology has produced. However, since technology in the area of portable batteries is advancing rapidly, five years after the charger is designed, it is no longer indicative of the state of the art. This gap in technology could result in obsolescence, and certainly a lack of ability to take advantage of the latest battery chemistry advances. As an example, consider a standard nickel cadmium battery. A battery pack designed five years ago with a specific battery cell size has a capacity 1.0 C. Today, the same size cells have 50% more capacity, or 1.5C. A charger designed five years ago to charge the five year old battery pack did so in 1 hour because the charge current it was designed to provide was equal to the C rate. Today's battery pack, made with the same size cells, now takes 11/2 hours to charge in the old charger since the C rate it provides is only two thirds the rate required to recharge the 1.5C battery in 1 hour. To some, taking longer to recharge a battery would be considered a step back in technology.
To buy an improved charger later would likely cost more than the original charger. However, this is the problem facing many large infrastructure consumers such as civil emergency, federal and local governments, and industrial corporations. When these types of customers buy a portable two way radio communications system and associated infrastructure, a significant portion of the cost is attributed to battery chargers for the batteries used on the portable radios. To repeat that expenditure every five years, or whenever a major battery technology advance occurs, is unreasonable.
From a customer perspective, existing battery charging systems are somewhat limiting with regard to how many battery suppliers participate in a given market. If an original equipment manufacturer (OEM) provides a static system, that is one that does not allow for changing technology over time, the customer is limited only to batteries that can be charged by that system. If a more advanced battery chemistry is made commercially available, the customer cannot take full advantage of batteries made with cells based on the new chemistry without incurring the expenses of buying chargers designed with optimized charge processes for the new chemical system. The cost of new chargers compatible with the new cell chemistry may make the purchase economically unviable.
For example, lithium ion battery packs were recently made available for some cellular phone models. These batteries are smaller, lighter, and offer more "talk time" compared to the existing nickel cadmium batteries. However, lithium ion batteries require a different charge regime than nickel cadmium batteries; a charge regime none of the existing chargers had been designed to provide. In that case, it was possible to provide the lithium ion batteries with electronics to make them "retrofittable". The additional cost of such electronics may not be prohibitive to an individual; however consider an industrial customer planning on purchasing several hundred batteries.
Therefore there exists a need for a battery charging system which can simultaneously charge a plurality of batteries having a variety of different capacities and based on a variety of different electrochemical systems. This system should be able to keep current with developing battery technology at minimum cost to a customer.